Personally, I don't even look at the general discussion sections on most forums. I'm "too boring" to have anything to talk about outside of the subject/focus of the forum in question, and tend to be well off the beaten path even within the forum's focus.
Like, I'm on a Harley forum, and have been for at least 10 years. I turn 38 this month, so I joined there around 28. There's also a yearly meetup we do in Eureka Springs, AR that I go to, and have gone to for the last 6 years (and 2 other forum meetups prior to that, been meeting up with these guys for 8 years now). Without me there, the average age is probably close to 64, and the next youngest regular after me is almost or soon to be 60. Last year in ES, I couldn't even really get in on the conversation, they're all talking about PSA numbers and bladder surgery and other old man problems. What do people my age talk about? Dunno. But even in the "biker" (V-twin cruiser specifically) crowd, I don't fit because I absolutely can't stand AC/DC or machismo dick-measuring. Are there people that ride Harleys that aren't like that? Sure, but they don't show up to bike nights.
My wife was talking to this guy we know, she mentioned how I had no friends, have issues with cabin fever but also no way to meet anyone because I hate sports and I hate "nerd culture" stuff (like TCGs, TTRPG/PnP-RPGs, etc) and the guy said "well what else is there?", as if The Breakfast Club had only Brian Johnson and Andy Clark (apparently all other personality tropes outside of "jock" and "nerd" have been deprecated).
Like, I like flowers. Not gardening, hate gardening, just like flowers. There's plenty of gardening forums, not so many flower ones. I like philosophy, but boy if you thought there were some tryhard pseudo intellectuals on pipe forums, it's nothing compared to those dump holes of quote mining and pedestrianism that's unrealized for being as such because those dorks don't know people to know how not deep their thoughts are. Watching this show "Numb3rs" lately, it's one of those Ridley Scott produced shows, so they try too hard to come off as smart and half the time get the concept wrong (to the point that it's annoying if you actually like math and logic)... well that's the kind of people that perpetuate the "intellectual" type forums. While on that subject... being into math is viewed as the most boring thing a person could be into. Guess what something I enjoy is? Yep, math.
Plus, look at this post, look at any post I make. They're always "too long". I can't leave well enough alone, if the answer is complex, I can't help but run through what I know, what I can extrapolate from what I do know, and what I can think of as possibilities at that moment. Apparently, nobody likes that, or very few.
I'm a buzzkill. Like if I ran through all I am into, people would maybe say I sound like an interesting person (I'm not), but then being "interesting" never translates into anyone being interested. So it kind of becomes this, "well, why should I bother starting a thread about X topic?", it's futility for me. Or looking at the off-topic section, nobody's talking about anything I'm interested in. And I don't have enough sentimentality for circle-jerking.
Like I could ask right now if anyone does nonograms. It'll probably be one of the least popular general discussion topics in the history of the forum.
As to others motives for not discussing many things, I haven't a clue.
